Question about isolating doubles

[Vie]

I imagine it would be hard to tell WHAT happened - so would one start with the tank valve first, and then move to the isolation valve if that didn't stop the gas leak?

If you have a post failure, it's usually easy to tell which side it is from the noise. If it's the right post, shut that off, "breath down" that side and switch to your back up.

If it's the left post, just shut it off and purge the gas out of the reg coming from that side. Reg in your mouth should be coming from your (working) right post so no need to switch

In either instance (right or left post failure), the bubbling/sound should stop. If the bubbling continues (i.e. it's a manifold or tank neck failure, not a post failure), turn off the isolator. The bubbling will continue, btw.

You should have signalled your buddy by this point (I would signal immediately, at the same time as I'm dealing with the problem) and he/she should then make sure that you've shut off the correct post (and check whether isolator needed shutting off). Your buddy then can determine whether the problem(s) can be fixed.

Note: Some divers/training agencies advocate shutting down the isolator first before dealing with either post.

 

[ianr33]

If you have a post failure, it's very easy to tell which side it is from the noise.

Not at all sure I believe that. Suppose a LP hose bursts just where it goes into the reg. Huge amount of bubbles and noise. Can you really tell which side is the problem?

Or what if the backup reg hose splits half way along the hose.Comes off the left post but leak will be on your right side.

I am in the isolate first camp ,unless it is obvious where the failure is ,then sort it out.

 

[JeffG]

Not at all sure I believe that. Suppose a LP hose bursts just where it goes into the reg. Huge amount of bubbles and noise. Can you really tell which side is the problem?

Had that happen (kinda...the reg fell off the hose) and yes I could tell that it was my backup hose, which is on the left post.

So the answer is yes, you can determine it for lots (but not all) cases.

 

[Vie]

Alright, will amend "very" to "usually"

 

[Walter]

Going for the isolator first wastes air that could be saved by shutting down the valve on the problem side. Chances of it being a problem that the isolator solves is extremely remote. Odds are more likely that the islolator will fail than it will be a tank neck o-ring or a burst disk problem. Isolator valves solve problems that don't really exist.

 

[wedivebc]

Going for the isolator first wastes air that could be saved by shutting down the valve on the problem side. Chances of it being a problem that the isolator solves is extremely remote. Odds are more likely that the islolator will fail than it will be a tank neck o-ring or a burst disk problem. Isolator valves solve problems that don't really exist.

I am of the isolator first mindset because if you have a hose failure near the 1st stage it will be very difficult to determine which side the massive flow of bubbles are from. Shutting the isolator as a first response secures a portion of your gas supply while you diagnose the problem.
If you always deal with a problem the same way your response time is greatly reduced.

 

[ArcticDiver]

...If you always deal with a problem the same way your response time is greatly reduced.

If it is the same problem; right on. But, when you don't know what the problem is the very first step is to Stop and Think. That may only take a second or two. But, that step puts order and control into handling the situation that automatic reaction does not.

 

[NorthWoodsDiver]

There is an argument that isolators are not really necessary, that is assuming you remove the burst disc which is against US DOT rules. Removing the isolator and replacing with a straight tube and removing the burst disc removes 2 places of failure. the argument against that is you could physically damage a valve also if diving doubles in overhead.

The other issue is finding the appropriate straight pipe to fit on your doubles.

regardless of reasoning it is far far more popular and the only recognized option by certification agencies in the US to just keep your isolator although disabling a burst disc is equally popular among tech divers but usually for a different reason.

 

[ScubaAndDreams]

Independent Doubles! Solves all your problems

(In all seriousness...take a course, there are argument for/against isolator first...I am of the offending valve first camp...)

 

[Vie]

The other issue is finding the appropriate straight pipe to fit on your doubles.

They don't make cheater bars anymore?